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<div class="moz-cite-prefix">On 28/11/22 6:53 pm, Adam Nielsen via
linux-aus wrote:<br>
</div>
<blockquote type="cite"
cite="mid:20221128175332.742d32ac@vorticon.teln.shikadi.net">
<pre class="moz-quote-pre" wrap="">As for the charger itself, if you look at the specs they list the
voltages and currents supported for USB PD. I think the Thinkpad wants
20 volts (although it may accept less, I don't know), and both chargers
you have linked to claim to output 20 volts in their specs, so in theory
they would work.
However without knowing the specs on the 30 W charger you have, it's
hard to say whether this is the problem. If the 30 W charger can't
output above 17 V then I'd suspect that could be why it doesn't work,
given a known good USB-C cable.</pre>
</blockquote>
<p>The other problem here is that the USB 3 PD spec has the charger
and the device talk to eachother to find out what power modes each
supports. At 20V there is one mode for 45-60W and another for
60-100W; a device capable of delivering 30W may well be in the 15V
range (27-45W). If the battery charging hardware requires greater
than 18V (the usual reason AFAIK for laptops to need 20V), then
it's just not going to turn on for a 15V charger.</p>
<p><a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Delivery">https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Delivery</a></p>
<p>If the new 30W charger does actually deliver 20V, then it's
under-spec - the minimum should be 45W. <br>
</p>
<p>Caveat: I am not a USB 3 expert :-)<br>
</p>
<blockquote type="cite"
cite="mid:20221128175332.742d32ac@vorticon.teln.shikadi.net">
<pre class="moz-quote-pre" wrap="">As more devices start to use USB PD, you may want to consider getting a
USB power monitor that supports PD, so you can plug it in between the
device and charger and actually see what's going on. These devices
will show the actual voltage and current on a small screen, so you can
see exactly what's going on and more easily compare different devices
and chargers. Here is an example I picked randomly from Aliexpress:</pre>
</blockquote>
<p>+1 for these devices, very handy. Make sure you also get one
that's bidirectional - I mistakenly got one that only shows
charging stats if it's plugged into the charger (i.e. the charger
has to have a socket, not a plug). Very annoying.</p>
<p>So why were we trying to get a low power charger? I don't find
the Thinkpad one very bulky... is it?</p>
<p>Have fun,</p>
<p>Paul<br>
</p>
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